Imaging member

ABSTRACT

An imaging member including, for example, a substrate, a charge blocking layer, an optional adhesive layer, a charge generating layer, a charge transporting layer comprising, and a film forming polymer binder substantially free of low molecular weight fractions.

BACKGROUND

[0001] The present invention is generally directed to imaging members,imaging apparatus, and processes thereof. More specifically, the presentinvention relates to multilayered electrophotographic imaging membershaving a novel charge transport layer composition comprising a chargetransport compound dissolved in a polymer, and wherein the low molecularweight fraction of the polymers has been selectively removed from thepolymer prior to charge transport layer preparation. The presentinvention also relates to processes for forming images on the member.

[0002] Typical imaging members include, for example: (1) photosensitivemembers or photoreceptors, which are commonly utilized inelectrophotographic imaging systems, such as, xerographic machines, and(2) electroreceptors, like ionographic imaging members, which are usedfor electrographic imaging systems. Imaging members are usuallyavailable in two forms, the rigid drum configuration and the flexiblebelt. The flexible imaging member belts may either be seamless or seamedbelts. Typical electrophotographic imaging member belts comprise animaging layer of a charge transport layer and a charge generating layercoated over one side of a flexible supporting substrate and an anti-curlback coating applied to the opposite side of the substrate to provideimaging member flatness. Electrographic imaging member belts aresomewhat simpler in structure; they typically comprise a dielectricimaging layer on one side of a flexible supporting substrate and mayalso have an anti-curl back coating on the opposite side of thesubstrate. A typical flexible imaging member belt has a ground stripcoated near one edge of the belt and adjacent to the imaging layer.

[0003] Photosensitive members having at least two electrically operativelayers provide electrostatic latent images when charged with a uniformnegative electrostatic charge, exposed to a light image and thendeveloped with finely divided electroscopic marking particles. Theresulting toner image is usually transferred to a suitable receivingmember such as paper.

[0004] As more advanced, higher speed electrophotographic imagingcopiers, duplicators and printers were developed, in some instances,degradation of image quality was encountered during extended cycling.Moreover, complex, highly sophisticated duplicating and printing systemsoperating at very high speeds have placed stringent requirementsincluding narrow operating limits on photoreceptors. Forelectrophotographic imaging members having flexible belt configuration,the numerous layers selected from photoconductive imaging members shouldbe highly flexible, adhere well to adjacent layers, and exhibitpredictable electrical characteristics within narrow operating limits toprovide excellent toner images over many thousands of cycles. One typeof multi-layered photoreceptor that has been employed as a belt inelectrophotographic imaging systems comprises a flexible supportsubstrate, a conductive layer, a blocking layer, an adhesive layer, acharge generating layer, a charge transport layer, and a conductiveground strip layer adjacent to one edge of the imaging layers. Thisphotoreceptor belt usually comprises an additional layer such as ananti-curl back coating on the back side of the support substrate inorder to provide the desired belt flatness.

[0005] Flexible photoreceptor belts are fabricated from sheets cut froman electrophotographic imaging member web stock. The cut sheets aregenerally rectangular in shape and all edges may be of the same lengthor one pair of parallel edges may be longer than the other pair ofparallel edges. The sheet is fabricated into a belt by joining theoverlapping opposite marginal end regions of the sheet. A seam istypically produced in the overlapping opposite marginal end regions atthe point of joining. Joining may be effected in any suitable manner,such as welding including for example ultrasonic processes, gluing,taping, pressure/heat fusing, and the like methods. However, ultrasonicseam welding is generally utilized in embodiments as the method ofjoining because it is rapid, clean, generally free of solventapplication, and produces a thin and narrow strong seam. The fabricatedflexible photoreceptor belt mounted around a multi-roller belt supportmodule and selected in an electrophotographic imaging machine mayundergo bending and flexing as the belt is dynamically cycled over theplurality of support and drive rollers of the belt support module.

[0006] In a machine service environment, a flexible imaging member belt,mounted on a belt supporting module, is generally exposed to repetitiveelectrophotographic image mechanical cycling which subjects the outerexposed anti-curl back coating to abrasion due to mechanical fatigue andinteraction with the belt drives and other support rollers as well assliding contact with backer bars. This repetitive cycling can lead to agradual deterioration in the physical/mechanical integrity of theexposed anti-curl backing layer. When the anti-curl back coating is wornthe thickness thereof is reduced and the anti-curl back coatingexperiences a loss of ability to counteract the tendency of imagingmembers upward curling which leads to the exhibition of belt curl-up atboth edges. Moreover, uneven wear of the anti-curl back coating has beenfound to cause early development of belt ripples which are ultimatelymanifested as copy printout defects. Thus, the anti-curl back coatingwear that results from mechanical contact interaction during dynamicimaging operations is a significant problem that shortens the servicelife of the belt and adversely affects image quality. Let it be pointedout here that anti-curl back coating wear is an unique problem only tothe imaging member belt configuration, since rigid imaging member drumsdo not require this coating.

[0007] Also, numerous other imaging members for electrostatographicimaging systems are known including selenium, selenium alloys, such asarsenic selenium alloys; layered inorganic imaging members, and layeredorganic members. Examples of layered organic imaging members includethose containing a charge transporting layer and a charge generatinglayer. Thus, for example, an illustrative layered organic imaging membercan be comprised of a conductive substrate, overcoated with a chargegenerator layer, which in turn is overcoated with a charge transportlayer. Examples of generator layers that can be employed in thesemembers include, for example, charge generator materials such as;selenium, cadmium sulfide, vanadyl phthalocyanine, x-metal freephthalocyanine, benzimidazole perylent (BZP), hydroxygalliumphthalocyanine (HOGaPc), chlorogallium phthalocyanine, and trigonalselenium dispersed in binder resin, while examples of transport layersinclude dispersions of various diamines, reference, for example, U.S.Pat. No. 4,265,990, the disclosure of which is incorporated herein byreference in its entirety.

[0008] A further mechanical problem associated with a photoreceptorbelt, comprising a charge generating layer and the charge transportlayer, is that the thickness of the outermost charge transport layertends to become thinner during image cycling as a result of wear. Thisdecrease in thickness may cause changes in the electrical performance ofthe photoreceptor. Thus, to maintain image quality, complex andsophisticated electronic equipment is of value in the imaging machine tocompensate for the electrical changes. This increases the complexity ofthe machine, cost of the machine, size of the footprint occupied by themachine, and the like. Without proper compensation of the changingelectrical properties of the photoreceptor during cycling, the qualityof the images formed can degrade due to spreading of the charge patternon the surface of the imaging member and result in a decline in imageresolution. High quality images are of value for digital copiers,duplicators, printers, and facsimile machines, particularly laserexposure machines that demand high resolution images.

[0009] There continues to be a need for improved imaging members, andimproved imaging systems utilizing such members. Additionally, therecontinues to be a need for imaging members having reduced transportlayer cracking in response to externally imposed tensile stress and withthe wear resistant enhanced outermost exposed layers, which members areeconomical to prepare and retain a number of their properties overextended time periods.

REFERENCES

[0010] In U.S. Pat. No. 5,830,614 to Pai et al, issued Nov. 3, 1998,there is disclosed a charge transport dual layer for use in a multilayerphotoreceptor comprising a support layer, a charge generating layer, anda charge transport layer comprising a first transport layer comprising acharge transporting polymer, and a second transport layer comprising acharge transporting polymer having a lower weight percent of chargetransporting segments than that of the charge transporting-polymer inthe first transport layer. Flexible electrophotographic imaging beltmembers may comprise a photoconductive layer comprising a single layeror composite layers. One type of composite photoconductive layer used inelectrophotography is illustrated in U.S. Pat. No. 4,265,990, whichdescribes a photosensitive member having at least two electricallyoperative layers. One layer comprises a photoconductive layer, which iscapable of photogenerating holes and injecting the photogenerated holesinto a contiguous charge transport layer. Generally, where the twoelectrically operative layers are supported on a conductive layer withthe photoconductive layer sandwiched between the contiguous chargetransport layer and the conductive layer, the outer surface of thecharge transport layer is normally charged with a uniform charge of anegative polarity and the supporting electrode is utilized as an anode.The supporting electrode however may still function as an anode when thecharge transport layer is sandwiched between the supporting electrodeand the photoconductive layer. The charge transport layer in this latterembodiment may be capable of supporting the injection of photogeneratedelectrons from the photoconductive layer and transporting the electronsthrough the charge transport layer.

[0011] In U.S. Pat. No. 4,410,616 to Griffiths et al., issued Oct. 18,1983, there is disclosed an improved ambipolar photoresponsive deviceuseful in imaging systems for the production of positive images, fromeither positive or negative originals, which device is comprised of: (a)supporting substrate, (b) a first photogenerating layer, (c) a chargetransport layer, and (d) a second photogenerating layer, wherein thecharge transport layer is comprised of a highly insulating organic resinhaving dissolved therein small molecules of an electrically activematerial of N,N′-diphenyl-N,N′-bis(“X substituted”phenyl)-[1,1,-biphenyl]-4,4′-diamine, wherein X is selected from thegroup consisting of alkyl and halogen.

[0012] U.S. Pat. No. 4,265,990 to Stolka et al, issued May 5, 1981,illustrates a photosensitive member having at least two electricallyoperative layers is disclosed. The first layer comprises aphotoconductive layer which is capable of photogenerating holes andinjecting photogenerated holes into a contiguous charge transport layer.The charge transport layer comprises a polycarbonate resin containingfrom about 25 to about 75 percent by weight of one or more of a compoundwith the specified general formula illustrated.

[0013] U.S. Pat. No. 6,242,144 describes a charge transport layerincluding an electrically inactive resin binder such as polycarbonateresin, polyester, polyarylate, polyacrylate, polyether, polysulfone, andthe like, with weight average molecular weights varying from about20,000 to about 150,000.

[0014] U.S. Pat. No. 6,020,096 illustrates a charge transport layerincluding any suitable electrically inert film forming polymeric bindersuch as poly(4,4′-isopropylidene-diphenylene)carbonate,poly(4,4′-isopropylidenediphenylene)carbonate,poly(4,4′-diphenyl-1,1′-cyclohexane carbonate), polyaryl ketones,polyester, polyarylate, polyacrylate, polyether, polysulfone, and thelike.

[0015] U.S. Pat. No. 6,171,741 describes that a photoreceptor includes acharge transport layer including an electrically inactive resinmaterial, for example, polycarbonate resins having a weight averagemolecular weight from about 20,000 to about 150,000. In embodiments,polycarbonate resins include poly(4,4′-dipropylidene-diphenylenecarbonate) with a weight average molecular weight of from about 35,000to about 40,000, available as LEXAN 1451υ from General Electric Company;poly(4,4′-isopropylidene-diphenylene carbonate) with a weight averagemolecular weight of from about 40,000 to about 45,000, available asLEXAN 141™ from General Electric Company; a polycarbonate resin having aweight average molecular weight of from about 50,000 to about 120,000,available as MAKROLON™ from Bayer Corporation; or a polycarbonate resinhaving a weight average molecular weight of from about 20,000 to about50,000 available as MERLON™ from Mobay Chemical Company. In specificembodiments, methylene chloride is a desirable component of the chargetransport layer coating mixture for adequate dissolving of all thecomponents and for its low boiling point.

[0016] Examples of electrophotographic imaging members having at leasttwo electrically operative layers, including a charge generator layerand diamine containing transport layer, are disclosed in U.S. Pat. No.4,265,990, U.S. Pat. No. 4,233,384, U.S. Pat. No. 4,306,008, U.S. Pat.No. 4,299,897 and U.S. Pat. No. 4,439,507, the disclosures thereof beingincorporated herein in their entirety.

[0017] The entire disclosures of these patents are incorporated hereinby reference.

SUMMARY

[0018] Disclosed herein is an electrophotographic imaging membercomprising a flexible supporting substrate having an electricallyconductive surface,

[0019] a hole blocking layer,

[0020] an optional adhesive layer,

[0021] a charge generating layer,

[0022] a hole transporting layer comprised of a solid solutioncomprising an organic hole transport dissolved in a film forming polymerbinder and which binder is free of low molecular weight fractions,wherein low represents a weight average molecular weight of from about1,000 to about 20,000 and a number average molecular weight of fromabout 1,000 to about 20,000 and

[0023] an anti-curl back coating.

[0024] Also disclosed is an improved positively chargedelectrophotographic imaging member comprising a film forming polymericbinder component and an organic electron transport compound in the holetransport layer wherein the polymeric component contains no lowmolecular weight fractions, wherein low represents a weight averagemolecular weight of from about 1,000 to about 20,000 and a numberaverage molecular weight of from about 1,000 to about 20,000.

[0025] Aspects illustrated herein relate to:

[0026] a substrate having a conductive surface,

[0027] an optional electron blocking layer,

[0028] an optional adhesive layer,

[0029] a charge generating layer,

[0030] an electron transporting layer comprising a film forming polymerbinder comprising no low molecular weight fractions, and furthercomprising an organic electron transport compound selected, for example,from the group consisting of a carboxlfluorenone malonitrile (CFM), anitrated fluoreneone,N,N′bis(dialkyl)-1,4,5,8-naphthalenetetracarboxylic diimide, andN,N′bis(diaryl)-1,4,5,8-naphthalenetetracarboxylic diimide,

[0031] 1,1′-dioxo-2-(aryl)-6-phenyl-4-(dicyanomethylidene)thiopyran,carboxybenzylnaphthaquinone, and

[0032] an anti-curl back coating.

[0033] Aspects illustrated herein relate to:

[0034] a substrate having an electrically conductive surface,

[0035] an optional charge blocking layer,

[0036] an optional adhesive layer,

[0037] an ambipolar layer comprising a polymer binder substantially freeof low molecular weight fractions, an organic hole transport compoundconsisting of an arylamine and an electron transporter selected, forexample, from the group consisting of a carboxlfluorenone malonitrile(CFM), a nitrated fluoreneone,N,N′bis(dialkyl)-1,4,5,8-naphthalenetetracarboxylic diimide,N,N′bis(diaryl)-1,4,5,8-naphthalenetetracarboxylic diimide, or

[0038] 1,1′-dioxo-2-(aryl)-6-phenyl-4-(dicyanomethylidene)thiopyran,carboxybenzylnaphthaquinone, diphenoquinone, and further comprising adispersion of photoconductive pigments, and

[0039] an anti-curl back coating.

[0040] The members may be imaged by depositing a uniform positiveelectrostatic charges on the imaging member, exposing the imaging memberto activating radiation in an image configuration to form anelectrostatic latent image, and developing the latent image withelectrostatically attractable marking particles to form a toner image inconformance to the latent image.

[0041] A typical negatively charged, multilayered electrophotographicimaging member or photoreceptor of a flexible belt configurationcomprises a flexible substrate support, a conductive surface layer, acharge (hole) blocking layer, an optional adhesive layer, a chargegenerating layer, and a charge (hole) transport layer, and an anti-curlback coating. The thickness of the substrate support depends on numerousfactors, including mechanical strength, flexibility, and economicalconsiderations; and thereby, this layer for a flexible belt may, forexample, have a thickness of from about 50 micrometers to about 150micrometers, and more specifically from about 75 micrometers to about125 micrometers.

[0042] The conductive surface layer over or coated on the substratesupport may vary in thickness from about 0.01 to about 1.0 micrometersdepending on the optical transparency and flexibility desired for theelectrophotographic imaging member. The conductive layer may be anelectrically conductive metal layer which may be formed, for example, onthe substrate by any suitable coating technique, such as, a vacuumdepositing or sputtering technique. Typical metals include aluminum,zirconium, niobium, tantalum, vanadium, hafnium, titanium, nickel,stainless steel, chromium, tungsten, molybdenum, and the like.

[0043] Any suitable blocking layer capable of forming an electronicbarrier to holes from the adjacent photoconductive or photogeneratinglayer and the underlying conductive layer may be utilized. The holeblocking layer may comprise nitrogen containing siloxanes or nitrogencontaining titanium compounds as disclosed, for example, in U.S. Pat.No. 4,291,110, U.S. Pat. No. 4,338,387, U.S. Pat. No. 4,286,033 and U.S.Pat. No. 4,291,110, the disclosures of these patents being incorporatedherein by reference in their entirety. The blocking layer may be appliedby any suitable conventional technique, such as, spraying, draw barcoating, gravure coating, silk screening, air knife coating, reverseroll coating, vacuum deposition, chemical treatment, and the like. Theblocking layer should be continuous and have a thickness of from about0.01 to about 0.2 micrometers.

[0044] An optional adhesive layer may be applied to the hole blockinglayer. Any suitable adhesive layer may be utilized. An adhesive layercomprising, for example, a linear saturated copolyester reaction productof four diacids and ethylene glycol may be utilized. This linearsaturated copolyester consists of alternating monomer units of ethyleneglycol and four randomly sequenced diacids in the above indicated ratioand has a weight average molecular weight of from about 70,000copolyester resin. Any adhesive layer employed should be continuous and,for example, have a dry thickness of from about 200 micrometers to about900 micrometers and, in embodiments from about 400 micrometers to about700 micrometers. Any suitable solvent or solvent mixtures may beemployed to form a coating solution of the polyester. Typical solventsinclude tetrahydrofuran, toluene, methylene chloride, cyclohexanone, andthe like, and mixtures thereof. Any other suitable and conventionaltechnique may be utilized to mix and thereafter apply the adhesive layercoating mixture to the hole blocking layer. Typical applicationtechniques include spraying, roll coating, wire wound rod coating, andthe like.

[0045] Any suitable charge generating layer may be applied to theadhesive layer, which can thereafter be overcoated with a contiguouscharge transport layer. Examples of charge generating layer materialsinclude, for example, inorganic photoconductive materials such asamorphous selenium, trigonal selenium, and selenium alloys selected fromthe group consisting of selenium-tellurium, selenium-tellurium-arsenic,selenium arsenide and mixtures thereof, and organic photoconductivematerials including various phthalocyanine pigment such as the X-form ofmetal free phthalocyanine, metal phthalocyanines such as vanadylphthalocyanine and copper phthalocyanine, quinacridones, dibromoanthanthrone pigments, benzimidazole perylene, substituted2,4-diamino-triazines, polynuclear aromatic quinones, and the likedispersed in a film forming polymeric binder. Selenium, selenium alloy,benzimidazole perylene, and the like and mixtures thereof may be formedas a continuous, homogeneous photogenerating layer. Benzimidazoleperylene compositions are well known and described, for example in U.S.Pat. No. 4,587,189, the entire disclosure of which is incorporatedherein by reference. Other suitable charge generating materials known inthe art may also be utilized, if desired. Any suitable charge generatingbinder layer may be utilized. Photoconductive particles for the chargegenerating binder layer such vanadyl phthalocyanine, metal freephthalocyanine, benzimidazole perylene, amorphous selenium, trigonalselenium, selenium alloys, such as, selenium-tellurium,selenium-tellurium-arsenic, selenium arsenide, and the like and mixturesthereof may be used, for example, because of their sensitivity to whitelight. Vanadyl phthalocyanine, metal free phthalocyanine and telluriumalloys may also be utilized, for example, because these materialsprovide the additional benefit of being sensitive to infrared light. Thephotogenerating materials selected should be sensitive to activatingradiation having a wavelength of from about 600 to about 700 nanometers.

[0046] Any suitable optional inactive resin material may be employed inthe charge generating binder layer including those described, forexample, in U.S. Pat. No. 3,121,006, the entire disclosure of which isincorporated herein by reference. Typical organic resinous bindersinclude thermoplastic and thermosetting resins, such as, polycarbonates,polyesters, polyamides, polyurethanes, polystyrenes, polyarylethers,polyarylsulfones, polybutadienes, polysulfones, polyethersulfones,polyethylenes, polypropylenes, polyimides, polymethylpentenes,polyphenylene sulfides, polyvinyl butyral, polyvinyl acetate,polysiloxanes, polyacrylates, polyvinyl acetals, polyamides, polyimides,amino resins, phenylene oxide resins, terephthalic acid resins, epoxyresins, phenolic resins, polystyrene and acrylonitrile copolymers,polyvinylchloride, vinylchloride and vinyl acetate copolymers, acrylatecopolymers, alkyd resins, cellulosic film formers, poly(amideimide),styrene-butadiene copolymers, vinylidenechloride-vinylchloridecopolymers, vinylacetate-vinylidenechloride copolymers, styrene-alkydresins, and the like.

[0047] The charge generating composition or pigment can be present inthe resinous binder composition in various amounts. Generally, fromabout 5 percent by volume to about 90 percent by volume of the chargegenerating pigment is dispersed in about 10 percent by volume to about95 percent by volume of the resinous binder, and in embodiments fromabout 20 percent by volume to about 30 percent by volume of the chargegenerating pigment is dispersed in about 70 percent by volume to about80 percent by volume of the resinous binder composition.

[0048] The charge generating layer ranges in thickness for example, offrom about 0.1 micrometers to about 5 micrometers, and in embodimentshas a thickness of from about 0.3 micrometers to about 3 micrometers.The charge generating layer thickness is related to binder content.Higher binder content compositions generally utilize thicker layers forcharge generation. Thicknesses outside these ranges may also beselected.

[0049] The charge, or hole transport layer may comprise any suitabletransparent organic polymer or non-polymeric material capable ofsupporting the injection of photo generated holes from the chargegenerating layer below and allowing the transport of these holes throughthe organic layer to selectively discharge the surface charge. Theactive hole transport layer not only serves to transport holes, but alsoprotects the photogenerating layer from abrasion or chemical attack andtherefor extends the operating life of the photoreceptor imaging member.The charge transport layer should exhibit negligible, if any, dischargewhen exposed to a wavelength of light of from about 4,000 angstroms toabout 9,000 angstroms. Therefore, the charge transport layer issubstantially transparent to radiation in a region in which thephotoconductor is to be used. Thus, the active hole transport layer is asubstantially non-photoconductive material but supports the injection ofphotogenerated holes from the generation layer. The active holetransport layer is normally transparent when exposure is effectedthrough the active layer to ensure that most of the incident radiationis utilized by the underlying charge carrier generator layer forefficient photogeneration. The hole transport layer in conjunction withthe generation layer in the instant invention is a material which is aninsulator to the extent that an electrostatic charge placed on the holetransport layer is not conducted in the absence of illumination.

[0050] The active hole transport layer may comprise any suitableactivating compound useful as an additive dispersed in electricallyinactive polymeric materials making these materials electrically active.These compounds may be added to polymeric materials which are incapableof supporting the injection of photogenerated holes from the generationmaterial and incapable of allowing the transport of these holestherethrough.

[0051] Any suitable arylamine hole transporter molecules may be utilizedin the hole transport layer. In embodiments, the hole transport layercomprises, for example, from about 35 percent to about 65 percent byweight of at least one hole transporting aromatic amine compound andabout 65 percent to about 35 percent by weight of a polymeric filmforming resin in which the aromatic amine is soluble to form a solidsolution hole transport layer. Typical aromatic amine hole transportingcompounds include, for example, triphenylmethane,bis(4-diethylamine-2-methylphenyl) phenylmethane;4′-4″-bis(diethylamino)-2′,2″-dimethyltriphenylmethane,N,N′-diphenyl-N,N′-bis(alkylphenyl)-[1,1′-biphenyl]-4,4˜-diamine whereinthe alkyl is, for example, methyl, ethyl, propyl, n-butyl, hexyl, etc.,N,N′-diphenyl-N,N′-bis(chlorophenyl)-[1,1′-biphenyl]-4,4′-diamine, andthe like, dispersed in an inactive film forming binder.

[0052] Examples of inactive resin binders include polycarbonate resin,polyvinylcarbazole, polyester, polyarylate, polyacrylate, polyether,polysulfone, and the like. Molecular weight average of a polymer bindercan vary, for example, from about 20,000 to about 1,500,000.

[0053] Any suitable and conventional technique may be utilized to mixand thereafter apply the hole transport layer coating mixture onto thecharge generating layer. Typical application techniques includespraying, extrusion die coating, roll coating, wire wound rod coating,and the like. Drying of the deposited coating may be effected by anysuitable conventional technique such as oven drying, infra red radiationdrying, air drying and the like. Generally, the thickness of thetransport layer is from about 5 micrometers and about 100 micrometers.

[0054] In embodiments, the ratio of the thickness of the chargetransport layer to the charge generator layer is, for example, fromabout 2.1 to 400:1, and more specifically from about 2:1 to about 200:1.

[0055] An anti-curl back coating may be applied to the back side of thesubstrate support (which is the side opposite the side bearing theelectrically active coating layers) to balance the curl and renderflatness. The anti-curl back coating may comprise any suitable organicor inorganic film forming polymers that are electrically insulating orslightly semi-conductive. In some cases, an anti-curl back coating maybe applied to the surface of the substrate opposite to that bearing thephotoconductive layer to provide flatness and/or abrasion resistancewhere a web configuration photoreceptor is fabricated. Overcoatings arecontinuous and typically have a thickness of less than about 10 microns,although the thickness can be outside this range. The thickness ofanti-curl backing layers generally is sufficient to balancesubstantially the total forces of the layer or layers on the oppositeside of the substrate layer. An example of an anti-curl backing layer isdescribed in U.S. Pat. No. 4,654,284, the disclosure of which is totallyincorporated herein by reference. A thickness of from about 70 to about160 microns is a typical range for flexible photoreceptors, although thethickness can be outside this range. An overcoat may have a thickness ofat most 3 microns for insulating matrices and at most 6 microns forsemi-conductive matrices. The use of such an overcoat can still furtherincrease the wear life of the photoreceptor, the overcoat having a wearrate of 2 to 4 microns per 100 kilocycles, or wear lives of from about150 to about 300 kilocycles.

[0056] The electron transporter selected for use either in thepositively charged or in the ambipolar single photoconductive insulatinglayer of the imaging member can be selected from for example, the groupconsisting of a carboxlfluorenone malonitrile (CFM) represented by:

[0057] wherein each R is independently selected from the groupconsisting of hydrogen, alkyl containing from about 1 to about 40 carbonatoms, alkoxy containing from about 1 to about 40 carbon atoms, phenyl,substituted phenyl, higher aromatic, for example, naphthalene andantracene, alkylphenyl containing from about 6 to about 40 carbons,alkoxyphenyl containing from about 6 to about 40 carbons, arylcontaining from about 6 to about 30 carbons, substituted aryl containingfrom about 6 to about 30 carbons and halogen,

[0058] a nitrated fluoreneone derivative represented by:

[0059] wherein each R is independently selected from the groupconsisting of hydrogen, alkyl containing from about 1 to about 40 carbonatoms, alkoxy containing from about 1 to about 40 carbon atoms, phenyl,substituted phenyl, higher aromatic, for example, naphthalene andantracene, alkylphenyl containing from about 6 to about 40 carbons,alkoxyphenyl containing from about 6 to about 40 carbons, arylcontaining from about 6 to about 30 carbons, substituted aryl containingfrom about 6 to about 30 carbons and halogen, and at least two R groupsare chosen to be nitro groups,

[0060] N,N′bis(dialkyl)-1,4,5,8-naphthalenetetracarboxylic diimidederivative, or N,N′bis(diaryl)-1,4,5,8-naphthalenetetracarboxylicdiimide derivative represented by:

[0061] wherein R₁ is substituted or unsubstituted alkyl, branched alkyl,cycloalkyl, alkoxy or aryl, for example, phenyl, naphthyl, or a higherpolycyclic aromatic, for example, anthracene R₂ is alkyl, branchedalkyl, cycloalkyl, or aryl, for example, phenyl, naphthyl, or a higherpolycyclic aromatic, for example, anthracene or the same as R₁; R₁ andR₂ can be chosen independently to have total carbon number from about 1to about 50 and in embodiments from about 1 to about 12. R₃, R₄, R₅ andR₆ are alkyl, branched alkyl, cycloalkyl, alkoxy or aryl, for example,phenyl, naphthyl, or a higher polycyclic aromatic such as anthracene orhalogen and the like. R₃, R₄, R₅ and R₆ can be the same or different. Inthe case where R₃, R₄, R₅ and R₆ are carbon, they can be chosenindependently to have a total carbon number from about 1 to about 50,but is in embodiments from about 1 and to about 12,1,1′-dioxo-2-(aryl)-6phenyl-4-(dicyanomethylidene)thiopyran derivativerepresented by:

[0062] wherein each R is independently selected from the groupconsisting of hydrogen, alkyl containing from about 1 to about 40 carbonatoms, alkoxy containing from about 1 to about 40 carbon atoms, phenyl,substituted phenyl, or higher aromatic, for example, naphthalene andantracene, alkylphenyl containing from about 6 to about 40 carbons,alkoxyphenyl containing from about 6 to about 40 carbons, arylcontaining from about 6 to about 30 carbons, substituted aryl containingfrom about 6 to about 30 carbons and halogen,

[0063] a carboxybenzylnaphthaquinone derivative represented by:

[0064] wherein each R is independently selected from the groupconsisting of hydrogen, alkyl containing from about 1 to about 40 carbonatoms, alkoxy containing from about 1 to about 40 carbon atoms, phenyl,substituted phenyl, higher aromatic, for example, naphthalene andantracene, alkylphenyl containing from about 6 to about 40 carbons,alkoxyphenyl containing from about 6 to about 40 carbons, arylcontaining from about 6 to about 30 carbons, substituted aryl containingfrom about 6 to about 30 carbons and halogen,

[0065] and a diphenoquinone represented by:

[0066] and mixtures thereof, wherein each R is independently selectedfrom the group consisting of hydrogen, alkyl containing from about 1 toabout 40 carbon atoms, alkoxy containing from about 1 to about 40 carbonatoms, phenyl, substituted phenyl, higher aromatic, for example,naphthalene and antracene, alkylphenyl containing from about 6 to about40 carbons, alkoxyphenyl containing from about 6 to about 40 carbons,aryl containing from about 6 to about 30 carbons, substituted arylcontaining from about 6 to about 30 carbons and halogen, and a filmforming binder.

[0067] The electron transporting materials contribute to the ambipolarproperties of the photoreceptor and can provide the desired rheology.Moreover, these electron transporting materials ensure substantialdischarge of the photoreceptor during image wise exposure to form theelectrostatic latent image.

[0068] The above materials can be processed into a dispersion useful forcoating by any of the conventional methods used to prepare suchmaterials. These methods include; ball milling, media milling (in bothvertical or horizontal bead mills), paint shaking the materials withsuitable grinding media, and the like to achieve a suitable dispersion.The photoconductive insulating layer may be prepared by any suitablemethod such as, for example, from a dispersion.

[0069] The photogenerating pigment particles, electron transportmolecules, and charge transport molecules coating mixture can be coatedby any suitable technique, for example, by using a spray coater,extrusion coater, roller coater, wire-bar coater, slot coater, doctorblade coater, gravure coater, and the like. Any suitable solvent may beutilized for coating. Typical solvents include, for example, ketones,alcohols, aromatic hydrocarbons, halogenated aliphatic hydrocarbons,ethers, amines, amides, esters, and the like. Specific examples ofsolvents include cyclohexanone, acetone, methyl ethyl ketone, methanol,ethanol, butanol, amyl alcohol, toluene, xylene, chlorobenzene, carbontetrachloride, chloroform, methylene chloride, trichloroethylene,tetrahydrofuran, dioxane, diethyl ether, dimethyl formamide, dimethylacetamide, butyl acetate, ethyl acetate, methoxyethyl acetate, and thelike. Since the crack resistant imaging members of the present inventioncan be prepared by a number of known coating methods, the coatingprocess parameters are dependent on the specific process, materials,coating component proportions, the final coating thickness desired, andthe like. Drying may be carried out by any suitable technique.Typically, drying is carried out at a temperature of from about 40degrees centigrade to about 200 degrees centigrade for a suitableperiod. Typical drying times include, for example, from about 5 minutesto about 10 hours under still or flowing air conditions.

[0070] The thickness of the single layer after drying can typically be,for example, from about 3 micrometers to about 50 micrometers and inembodiments, from about 5 micrometers to about 40 micrometers. Themaximum thickness of the photoconductive insulating layer in any givenembodiment is dependent primarily upon factors such as photosensitivity,electrical properties and mechanical considerations.

[0071] The imaging member may by employed in any suitable process suchas, for example, copying, duplicating, printing, faxing, and the like.Typically, an imaging process may comprise forming a uniform charge onthe imaging member of the present invention, exposing the imaging memberto activating radiation in image configuration to form an electrostaticlatent image, developing the latent image with electrostaticallyattractable marking material to form a marking material image, andtransferring the marking material image to a suitable substrate. Ifdesired, the transferred marking material image may be fixed to thesubstrate or transferred to a second substrate. Electrostaticallyattractable marking materials are known and comprise, for example, athermoplastic resin, a colorant, such as a pigment, a charge additive,and surface additives. Typical marking materials are disclosed in U.S.Pat. No. 4,560,635; U.S. Pat. No. 4,298,697 and U.S. Pat. No. 4,338,390,the entire disclosures thereof being incorporated herein by reference.Activating radiation may be from any suitable device such as anincandescent light, image bar, laser, and the like. The polarity of theelectrostatic latent image on the imaging member of the presentinvention may be positive or negative.

[0072] The invention will further be illustrated in the followingnon-limiting working examples, it being understood that these examplesare intended to be illustrative only and that the invention is notintended to be limited to the materials, conditions, process parametersand the like recited herein.

COMPARATIVE EXAMPLE

[0073] An electrophotographic imaging member web stock was prepared byproviding a 0.02 micrometers thick titanium layer coated on a biaxiallyoriented polyethylene naphthalate substrate (KALADEX™, available fromDupont, Inc.) having a thickness of 3.5 micrometers (89 micrometers) andapplying thereto, using a gravure coating technique a solutioncontaining 10 grams gamma aminopropyltriethoxy silane, 10.1 gramsdistilled water, 3 grams acetic acid, 684.8 grams of 200 proof denaturedalcohol and 200 grams heptane. This layer was then allowed to dry for 5minutes at 135 degrees Celsius in a forced air oven. The resulting holeblocking layer of nitrogren containing siloxanes had an average drythickness of 0.05 micrometers as measured with an ellipsometer.

[0074] An adhesive interface layer was then prepared by extrusionapplication to the hole blocking layer of nitrogen containing siloxanes,a wet coating containing 5 percent by weight based on the total weightof the solution of a polyester adhesive (MOR-ESTER 49,000™, availablefrom Morton International, Inc.) in a 70:30 volume ratio mixture oftetrahydrofuranlcyclohexanone. The adhesive interface layer was allowedto dry for 5 minutes at 135 degrees Celsius in the forced air oven. Theresulting adhesive interface layer of MORESTER in tetrahydrofuranlcyclohexane had a dry thickness of 0.065 micrometers.

[0075] The adhesive interface layer was thereafter coated with aphotogenerating layer. The photogenerating layer dispersion was preparedby introducing 0.45 grams of IUPILON 200™poly(4,4′-diphenyl)-1,1′-cyclohexane carbonate, available fromMitsubishi Gas Chemical Corp., and 50 milliliters of tetrahydrofuraninto a 4 ounce glass bottle. To this solution was added 2.4 grams ofhydroxygallium phthalocyanine and 300 grams of ⅛ inch (3.2 millimeters)diameter stainless steel shot. This mixture was then placed on a ballmill for 20 to 24 hours. Subsequently, 2.25 grams ofpoly(4,4′-diphenyl)-1,1′-cyclohexane carbonate was dissolved in 46.1grams of tetrahydrofuran, then added to this hydrogallium phthalocyanineslurry. This slurry was then placed on a shaker for 10 minutes. Theresulting slurry was, thereafter, coated onto the adhesive interface byextrusion application process to form a layer having a wet thickness of0.25 milliliters. However, a strip about 10 millimeters wide along oneedge of the substrate web bearing the blocking layer and the adhesivelayer was deliberately left uncoated by any of the photogenerating layermaterial to facilitate adequate electrical contact by the ground striplayer that was applied later. This photogenerating layer was dried at135 degrees Celsius for 5 minutes in a forced air oven to form a drythickness photogenerating layer having a thickness of 0.4 micrometerlayer.

[0076] This coated imaging member was simultaneously overcoated with ahole transport layer and a ground strip layer using extrusion co-coatingprocess. The hole transport layer was prepared by introducing into anamber glass bottle a weight ratio of 1:1 organic hole transport moleculeN,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4-4′-diamine andpoly(4,4′-isopropylidene diphenyl carbonate), having a weight averagemolecular weight of about 120,000, commercially available as MAKROLON5705™, from Bayer A.G. The resulting mixture was dissolved to give a 15percent by weight solid in 85 percent by weight methylene chloride. Thissolution was applied onto the photogenerator layer to form a coatingwhich upon drying gave a hole transport layer diamine thickness of 29micrometers.

[0077] The approximately 10 millimeter wide strip of the adhesive layerleft uncoated by the photogenerator layer was coated over with a groundstrip layer of aluminum during the co-coating process. This ground striplayer, after drying along with the co-coated hole transport layer at 135degrees Celsius in the forced air oven for about 5 minutes, had a driedthickness of about 19 micrometers. This ground strip is electricallygrounded by conventional means, such as, a carbon brush contact duringconventional xerographic imaging process. The imaging member, ifunrestrained, at this point, did exhibit spontaneous upward curling intoa 1½ inch roll.

[0078] An anti-curl coating was prepared by combining 8.82 grams ofpolycarbonate resin (MAKROLON 5705™, available from Bayer AG), 0.72 gramof polyester resin (VITEL PE-200™, available from Goodyear Tire andRubber Company) and 90.1 grams of methylene chloride in a glasscontainer to form a coating solution containing 8.9 percent solids. Thecontainer was covered tightly and placed on a roll mill for about 24hours until the polycarbonate and polyester were dissolved in themethylene chloride to form the anti-curl coating solution. The anti-curlcoating solution was then applied to the rear surface (side opposite thephotogenerator layer and hole transport layer) of the imaging member webstock, again by extrusion coating process, and dried at 135 degreesCelsius for about 5 minutes in the forced air oven to produce a driedfilm thickness of about 17 micrometers and render flatness. Theresulting electrophotographic imaging member for negative chargingsystem was used to serve as an imaging member control.

EXAMPLE I

[0079] Two hole transport layer solutions were prepared according to theprocedures described in the Comparative Example, but with the exceptionthat the MAKROLON™ in one of these coating solutions was by a processingto effect the removal or elimination of the low molecular weightfraction from the polymer prior to coating solution preparation, whereinlow represents a weight average molecular weight of from about 1,000 toabout 20,000 and a number average molecular weight of from about 1,000to about 20,000. These coating solutions were each coated over areleasing surface of a thick polyvinyl fluoride substrate and dried at135 degrees Celsius to remove the layer of methylene chloride yieldingtwo, 30 micrometer thick hole transport layers. The process adopted forremoval of low molecular weight fraction was carried out by firstdissolving the MAKROLON™, as received from Bayer, in methylene chlorideto form a solution followed by gradual addition of methanol (a nonsolvent) to the solution to effect the precipitation of the highmolecular weight component of the polymer from the solution, whereinhigh represents a weight average molecular weight of from about 20,000to about 120,000 and a number average molecular weight of from about20,000 to about 120,000. The precipitates were then filtered and driedto provide the MAKROLON™.

[0080] Mechanical properties of these two layers showed that theelimination of the low molecular weight fraction from MAKROLON™ couldeffectively increase the break elongation and the break stress of thetransport layer.

EXAMPLE II

[0081] An electrophotographic imaging member was prepared according tothe procedures and using the same material as that described inComparative Example, with the exception that the hole transport layer aswell as the anti-curl back coating were prepared with the precipitatedMAKROLON™ of Example I. The prepared imaging member and the imagingmember of Comparative Example were cut to give 1 inch×6 inch samples,each were subjected to low speed sample tensile elongation, using anInstron Mechanical Tester. The exact extent of stretching at which onsetof hole transport layer cracking became evident was analyzed under 100×magnification with a stereo optical microscope. The hole transport layercracking strains observed was about 3.25 percent for the ComparativeExample and about 4 percent for the corresponding imaging member usingprecipitated MAKROLON™ in the hole transport layer.

[0082] Since removal of low molecular weight fraction did not alter thechemical make-up of the polymer, but merely improved its mechanicalstrength and crack resistance, no deleterious photo-electrical impactwas evident.

Dynamic Mechanical Testing Results

[0083] The electrophotographic imaging member web stocks of theComparative Example and Example II were each cut to give rectangularsheets having precise dimensions of 440 millimeters width and 2,808millimeters in length. Each cut imaging member sheet was ultrasonicallywelded to form a seamed flexible imaging member belt for dynamic fatigueelectrophotographic imaging and print testing in a xerographic machine,employing a belt cycling module utilizing four 49 millimeter diameter,three 32.7 millimeter diameter, and one small 24.5 millimeter diameterbelt support rollers. The belt cycling test results obtained showed thatthe onset of fatigue in the hole transport layer was significantlyextended by a factor of about 2½ times for the belt prepared from theimaging member of Example II compared to that of the belt prepared fromthe imaging member of the Comparative Example. The delay of transportlayer cracking was further established for the member of Example I bystatic bend-parking over a 19 millimeter diameter roller using amethylene chloride vapor exposure test.

[0084] The electrophotographic imaging members of the ComparativeExample and Example II were cut to a size of 1 inch (2.54 centimeters)by 12 inches (30.48 centimeters) and tested for resistance to wear usinga dynamic mechanical cycling device in which glass tubes were skiddedacross the surface of the hole transport layer on each imaging member.

[0085] The extent of the hole transport layer wear was measured using apermascope at the end of a 330,000 wear cycle tests. The wear resistanceof the anti-curl back coating was also tested as described bypositioning each test sample such that the anti-curl back coating wasfacing the sliding glass surface to effect wear contact.

[0086] The wear resistance testing results obtained for the holetransport layer and the anti-curl back coating were consistentlyenhanced by about 40 percent using precipitated MAKROLON™, for example,a control hole transport layer thickness was 30 micrometers beforetesting and 19 micrometers after 330,000 wear cycles test. Using theprecipitated MAKROLON, the hole transport layer thickness was 30micrometers before and 23.4 micrometers after 330,000 wear cycles.

[0087] The control anti-curl backing coating thickness was 17micrometers before and 7.5 micrometers after 330,000 wear cycles test.Using the precipitated MAKROLON, the anti-curl back coating thicknesswas 17 micrometers before testing and 11.1 micrometers after 330,000wear cycles.

[0088] Although the invention has been described with reference tospecific embodiments, it is not intended to be limited thereto. Rather,those having ordinary skill in the art will recognize that variationsand modifications, including equivalents, substantial equivalents,similar equivalents, and the like may be made therein which are withinthe spirit of the invention and within the scope of the claims.

What is claimed is:
 1. A member comprising: a substrate; a chargeblocking layer; an optional adhesive layer; a charge generating layer; acharge transport layer comprising a charge transport component and abinder; and an anti-curl back coating comprising a polymer and whereinthe polymer is substantially free of low molecular weight fractions. 2.A member according to claim 1, wherein the charge transport layer bindercomprises a polymer comprising high molecular weight fractions andwherein the binder is present in an amount of from about 45 to about 55weight percent based on the total weight of the charge transport layer.3. A member according to claim 1, wherein the binder is selected fromthe group consisting of polycarbonate, polyvinylcarbazole, polyester,polyarylate, polyacrylate, polyether, and polysulfone, and wherein highrepresents a weight average molecular weight of from about 20,000 toabout 120,000 and a number average molecular weight of from about 20,000to about 120,000.
 4. A member according to claim 1, wherein the chargetransport layer contains the binder in an amount of from about 30 toabout 90 weight percent based on the total weight of the chargetransport layer.
 5. A member according to claim 1, wherein the chargetransport layer binder comprises a polymer containing high molecularweight fractions and wherein the binder is present in an amount of fromabout 45 to about 55 weight percent based on the total weight of thecharge transport layer.
 6. A member according to claim 1, wherein thecharge transport layer comprises a binder selected from the groupconsisting of bisphenol A polycarbonate, poly(4,4′-isopropylidenediphenyl) carbonate, and poly(4,4′-diphenyl)-1,1′-cyclohexane carbonate.7. A member according to claim 1, wherein the binder is substantiallyfree of low molecular weight fractions, and wherein low is from about1,000 to about 20,000.
 8. A member according to claim 7, wherein thebinder contains a polymer with a molecular weight distribution of fromabout 50,000 to about 120,000.
 9. A member according to claim 1, whereinthe binder used in the charge transport layer further comprisespoly(4,4′-diphenyl)-1,1′-cyclohexane carbonate.
 10. A member accordingto claim 1, wherein the charge transport layer further comprises anelectron transport component selected from the group consisting ofcarboxlfluorenone represented by:

wherein each R is independently selected from the group consisting ofhydrogen, alkyl, alkoxy, aryl and halogen, a nitrated fluoreneonerepresented by:

wherein each R is independently selected from the group consisting ofhydrogen, alkyl, alkoxy, aryl and halogen, and wherein at least two Rgroups are nitro, N,N′bis(dialkyl)-1,4,5,8-naphthalenetetracarboxylicdiimide, or a N,N′bis(diaryl)-1,4,5,8-naphthalenetetracarboxylic diimiderepresented by:

wherein R₁ is alkyl, alkoxy or aryl, R₂ is alkyl, or aryl; R₁, R₂, R₃,R₄, R₅ and R₆ are selected from the group consisting of alkyl, alkoxy,and halogen.
 11. A member according to claim 1, wherein the chargetransport layer contains an electron transport layer comprising:1,1′-dioxo-2-(aryl)-6-phenyl-4-(dicyanomethylidene)thiopyran representedby:

wherein each R is independently selected from the group consisting ofhydrogen, alkyl containing from about 1 to about 40 carbon atoms, alkoxycontaining from about 1 to about 40 carbon atoms, phenyl, substitutedphenyl, naphthalene and antracene, alkylphenyl containing from about 6to about 40 carbons, alkoxyphenyl containing from about 6 to about 40carbons, aryl containing from about 6 to about 30 carbons, substitutedaryl containing from about 6 to about 30 carbons and halogen.
 12. Amember according to claim 1, wherein the charge transport layer containsan electron transport component comprising: acarboxybenzylnaphthaquinone derivative represented by:

wherein each R is independently selected from the group consisting ofhydrogen, alkyl, atoms, alkoxy, aryl and halogen; a diphenoquinonerepresented by:

and mixtures thereof, wherein each R is independently selected from thegroup consisting of hydrogen, alkyl, alkoxy, aryl and halogen.
 13. Amember according to claim 1, wherein the charge transport layercomprises a hole transport component comprising an aryl aminerepresented by:

wherein X is selected from the group consisting of alkyl and halogen.14. A member according to claim 13, wherein the arylamine isN,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine. 15.A member according to claim 13, wherein the arylamine isN,N′-diphenyl-N,N′-bis(4-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine. 16.A member according to claim 1, wherein the charge transport layercomprises a charge transport component in an amount of from about 10 toabout 70 weight percent based on the total weight of the chargetransport layer.
 17. A member according to claim 10 wherein the chargetransport layer has a weight ratio of the charge transport molecule tothe binder of from about 10:90 to about 70:30.
 18. A member according toclaim 1, wherein the hole transport layer comprisespoly(4,4′-diphenyl)-1,1′-cyclohexane andN,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine in aweight ratio of the binder to hole transport is from about 90:10 toabout 30:70.
 19. A member according to claim 13, wherein the holetransport is selected from the group consisting ofN,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′diamine;N,N′-diphenyl-N,N′-bis(4-methylphenyl)-[1,1′-biphenyl]-4,4′diamine;N,N′-diphenyl-N,N′-bis(alkylphenyl)1,1′-biphenyl-4,4′-diamine;Tritolylamine; N,N′-bis-(3,4-dimethylphenyl)-4-biphenyl amine;N,N′-bis-(4-methylphenyl)-N,N″-bis(4-ethylphenyl)-1,1′-3,3′-dimethylbiphenyl)-4,4′-diamine;phenanthrene diamine, and stilbene molecules.
 20. A member according toclaim 1, wherein the charge generating layer has a thickness of fromabout 0.1 micrometer to about 5 micrometers.
 21. A member according toclaim 1, wherein the charge generating layer comprises from about 10percent to about 95 percent by volume of the binder, based on the totalvolume of the charge generating layer.
 22. A member according to claim1, wherein the charge generating layer comprises from about 80 percentto about 70 percent by volume of the binder, based on the total volumeof the charge generating layer.
 23. A member comprising: an ambipolarlayer comprising a hole transport component, an electron transportcomponent, a photogenerating component and a film forming resin binderwherein the binder comprises a polymer substantially free of lowmolecular weight fractions; and an anti-curl back coating.
 24. A memberaccording to claim 23, wherein the ambipolar layer comprises from about5 percent to about 50 percent by weight of an arylamine hole transport,about 1 percent to about 40 percent by weight of an electron transport,about 0.05 percent to about 30 percent by weight of photogeneratingpigment, and wherein the ambipolar layer further comprises a polymerbinder substantially free of low molecular weight fractions, and whereinlow represents a weight average molecular weight of from about 1,000 toabout 20,000 and a number average molecular weight of from about 1,000to about 20,000.
 25. A member according to claim 23, wherein theambipolar layer comprises from about 20 percent to about 40 percent byweight of the arylamine hole transport, about 5 percent to about 30percent by weight electron transporter, and wherein the ambipolar layerfurther comprises a polymer binder free of low molecular weight polymerfractions, and wherein low is from about 5,000 to about 20,000 and whichlayer comprises high molecular weight fractions of polycarbonate.
 26. Animaging process comprising: providing a member comprising, a supportlayer; a photogenerator layer, and a binder wherein the binder comprisesa polymer substantially free of low molecular weight fractions.
 27. Amember according to claim 1 and containing an adhesive layer comprisinga linear saturated co-polyester reaction product of diacids and ethyleneglycol and having a thickness of from about 200 micrometers to about 900micrometers.
 28. A member according to claim 27 wherein the adhesivelayer has a thickness of from about 400 micrometers to about 700micrometers.
 29. A member according to claim 1 wherein the substratecomprises a biaxially oriented polyethylene naphthalate substrate andwherein the thickness is from about 50 to about 150 micrometers.
 30. Amember according to claim I wherein the anti-curl polymer is selectedfrom the group consisting of polyester, polyarylate, polysulfone,polyethersulfone, polyetherimide, polycarbonate, andpolystyrene-acrylonitrile and has a thickness of from about 50 to about200 microns.
 31. A member according to claim 1 wherein the blockinglayer comprises nitrogen containing siloxanes.
 32. A member according toclaim 1 wherein the blocking layer comprises nitrogen containingtitanium.